Glossary of Terms Used in a Sleep Report
Apnea Index (AI)—The averaged number of apneas per hour of sleep.
Hypopnea Index (HI)—The averaged number of hypopneas per hour of sleep.
Oximetry—Measurements of oxygen saturation in the blood, assessed with each heartbeat. The low value is the nadir noted.
MSLT Report—Multiple Sleep Latency Test. Report of sleep latencies (onsets), and REM latencies measured across multiple naps at 2 hour intervals during the day.
PLMS Index—The averaged number of PLMS per hour of sleep.
REM Latency (RL)—Minutes elapsed from SO to REM sleep.
REM Sleep—Dream sleep.
Standard Report—Study for the entire night without intervention.
Sleep Latency (SL)—The amount of time from LO to Sleep Onset (SO).
Split-night Report—Full night study mathematically divided into two parts, one without therapeutic action, the other with (such as intervention with NCPAP).
Stage 1 sleep—Light sleep.
Stage 2 Sleep—Quiet sleep.
Stage 3 Sleep—Quiet, deeper sleep.
Stage 4 Sleep—Deep sleep.
Respiratory Disturbance Index (RDI)—The averaged number of apneas AND Hypopneas per hour of sleep.
Sleep Efficiency Index (SEI)—Index to compare sleep to wakefulness. The higher the value, the more sleep the person achieves.
Total Central Apneas—Number of times complete cessation of breath is noted, lasting 10 seconds or longer, without effort to breathe.
Total Hypopneas—Number of times partial cessation of breath is noted, lasting 10 seconds or longer. Partial cessation implies continued effort to breathe. Underlying disease processes may effect the implication.
Total Obstructive Apneas—Number of times complete cessation of breath is noted lasting 10 seconds or longer, with continued effort to breathe.
Total Periodic Limb Movements in Sleep (PLMS)—The number of muscular ‘twitches’ lasting at least one half of a second, occurring in episodes of 4 or more within 90 seconds of each other.
Total Recording Time (TRT)—Time in minutes from Lights Out (Start) to Lights On (End).
Total Sleep Time (TST)—TRT minus the time spent in wakefulness.
Total Wake Time (TWT)—Minutes of wakefulness
